This invention relates to an endoscopic method. More particularly, this invention relates to a method utilizable with endoscopes to insert working instruments into a patient. This invention also relates to an associated instrument assembly. The invention is useful, for instance, in the treatment of Barrett's Esophagus and sessile colonic polyps.
The precancerous nature of high-grade dysplasia and the difficulty in detection of invasive carcinoma by endoscopy make esophagectomy and ablative therapy important considerations to treating those patients with this serious condition. The gold standard treatment for early esophageal cancer and high grade dysplasia is esophagectomy, the surgical removal of the diseased segment of the esophagus. This is an effective but drastic treatment and presents significant complications and lifestyle problems for the patient. Many patients are poor surgical candidates for this difficult surgery.
Endoscopic mucosal resection (EMR), the removal of mucosal tissue by use of a snare, is a therapeutic alternative and has become a standard treatment for patients with Barrett's Esophagus. This technique preserves the patient's esophagus while resecting the mucosa that is affected by this disease. A second method is tissue ablation with heat therapy. EMR is superior to tissue destruction because it permits pathologic evaluation of the resected specimen. Current endoscopic mucosal resection techniques for the treatment of esophageal cancer include strip biopsy, double snare polypectomy, with the combined use of saline and epinephrine injection. EMR may be curative if the primary tumor or dysplastic tissue is removed completely.
Another area where EMR may be used is for removal of large sessile polyps in the GI tract, primarily the colon. The malignant transformation potential of colorectal adenomatous polyps is well documented. Colonoscopic polypectomy is widely practiced in order to prevent the development of colon cancer. Sessile polyps are premalignant lesions that lay flatly on the mucosal surface of the colon wall. These lesions, in contrast to pedunculated polyps, are devoid of a stalk, and are broad based. The colon wall is composed of several layers: the mucosa (the surface layer), the submucosa, the muscularis (muscle layer), and the serosa (connective tissue layer). The thickness of the entire wall is 5 mm. When a cautery snare is used to remove a larger sessile lesion, it may catch part of the muscularis layer Cutting through the muscle layer causes a colonic perforation.
Devices currently used for EMR procedures are polypectomy snares and a variety of devices to assist in the use of these snares. For resection of dysplastic tissue in the esophagus the technique involves using two snares, one to hold up the targeted tissue and the other to sever that tissue. The use of saline solutions for injection beneath the target tissue is a common practice for the purpose of raising the tissue and creating a buffer layer. This process is called saline assisted polypectomy (SAP).
In the case of sessile colonic polyps, SAP is standard medical practice. The raised polyp is then severed with a polypectomy snare, often in several segments (segmental resection) depending on the size and location of the polyp.
The depth of the cut that occurs using the snare cautery device to remove dysplastic mucosal tissue is critical. As discussed above, if the cut is too deep, injuring the muscularis layer, a perforation may occur. Conversely, a cut too shallow may not remove enough of the affected tissue and therefore may require additional procedures, or worse, result in the development of metastatic cancer. Similar complications may occur during the removal of sessile colonic polyps. The colonic wall is approximately the same thickness as the esophageal wall, namely 5 mm. A perforation as a result of cutting into the muscularis layer will cause a colonic perforation, while a lesion that is not completely removed, either due to insufficient depth or breath, will result in recurrence of the dysplastic tissue. Repeated resections after a certain interval are recommended if the margin of resection achieved during the procedure is too close to the tumor. More than 2 mm of cancer clearance is required. The complications resulting from EMR as performed with today's devices and methods include perforation, bleeding, and strictures that occur from scar formation resulting from EMR procedures.
Ablation techniques rely on chemicals which, when combined with heat or freezing, destroy dysplastic tissue. Adverse reactions include destruction of the healthy tissue surrounding the lesion, allergic reactions to the chemicals and sensitivity to sun-light. Furthermore, all ablative techniques destroy the tissue and prevent adequate pathologic examination of the specimen.
An important limitation of surgical procedures performed through a flexible endoscope is the narrow working channel. Most endoscopes have a working channel with a diameter ranging from 2.3 to 3.4 millimeters in diameter. Thus, the instruments that one may pass through this channel must have an outer diameter smaller than the diameter of the working channel. In addition, the endoscope may go through convolutions and bends in the gastrointestinal tract, necessitating that the instrument be flexible. More specifically, the stiff length capable of being passed through an endoscope is 1.5 centimeters.
In the present state of the art, if a working distal end is required, which has a larger diameter than the working channel; such an instrument is affixed to the outer wall of the endoscope shaft, and passed into the patient alongside the endoscope. This makes for a much larger instrument which, in certain cases must be passed through the mouth, into the esophagus and stomach of the patient. Because the entryway into the esophagus does not accommodate such a large instrument, complications from passing such larger instrument abound. These include tearing of the upper esophageal sphincter muscle, and esophageal lacerations and perforations. Patients that undergo such invasive procedures require general anesthesia, and lengthier post operative care. These interventional procedures may only be performed by a handful of specialists, and are not available to the gastroenterologists at large. It would therefore be advantageous if one could find a way to advance an instrument with a larger working distal end into the gastrointestinal tract, and still be able to operate with such a device through the working channel of an endoscope.